5-Minute Emergency Consult
Opportunistic Infections
Basics
Description
Description
Unusual infections that occur when host suffers a decrease in resistance against normally nonpathogenic organisms
Etiology
Etiology
- Occurs in HIV patients when the CD4 T-lymphocyte count falls below 200 cells/mm3 or <14% of the total lymphocyte count:
- Pneumocystis jirovecii pneumonia (PCP)
- Disseminated tuberculosis
- Cryptosporidiosis
- Microsporidiosis
- Isosporiasis
- Toxoplasmosis
- Histoplasmosis
- Cryptococcosis
- Mycobacterium avium complex
- Tuberculosis pericarditis or meningitis
- Cytomegalovirus
- Human herpesvirus-8 (Kaposi sarcoma)
- JC virus (progressive multifocal leukoencephalopathy)
- Hepatitis B virus
- Penicilliosis marneffei
- Bacterial species
- Cell-mediated deficiency:
- Hematologic malignancies
- Lymphoma
- High-dose glucocorticoid therapy
- Autoimmune disorders
- Viral infections
- Cytotoxic drugs/chemotherapy
- Radiation therapy
- Associated with:
- Legionella
- Nocardia
- Salmonella
- Mycobacteria
- Neutrophil impairment/depletion:
- Cytotoxic drugs
- Aplastic anemia
- Drug reactions:
- Dapsone
- Neoplastic invasion of bone marrow
- Arsenic
- Penicillin
- Chloramphenicol
- Procainamide
- Vitamin deficiencies
- Associated with:
- Staphylococcus and α-hemolytic Streptococcus
- Enteric organisms and anaerobes
- Invasive aspergillosis
- Immunomodulatory drugs:
- TNF-α inhibitors
- Inflixamab > etanercept
- Rituximab
- Adalimumab
- Azathioprine
- TNF-α inhibitors
- Consider hepatitis, Herpes zoster and M. tuberculosis reactivation
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Citation
Schaider, Jeffrey J., et al., editors. "Opportunistic Infections." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307680/all/Opportunistic_Infections.
Opportunistic Infections. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307680/all/Opportunistic_Infections. Accessed November 3, 2025.
Opportunistic Infections. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307680/all/Opportunistic_Infections
Opportunistic Infections [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2025 November 03]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307680/all/Opportunistic_Infections.
* Article titles in AMA citation format should be in sentence-case
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T1 - Opportunistic Infections
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ED - Hayden,Stephen R,
ED - Wolfe,Richard E,
BT - 5-Minute Emergency Consult
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PB - Lippincott Williams & Wilkins
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DB - Emergency Central
DP - Unbound Medicine
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